The current air conditioning system is a marine air conditioning system for use in boats having enclosed cabins. Such systems in the prior art may be permanently installed or portable. The permanent systems are typically found on larger boats, while the portable systems are used on smaller boats.
Most permanently installed marine air conditioning systems are based on a conventional refrigeration cycle. Air from an enclosed cabin on a boat is blown through a cooling coil cooled with a refrigerant gas such as freon. A compressor is used to compress the freon. The cooling coil reduces the temperature of the air passing over it, and also causes water vapor carried by the air to condense on the cooling coil. Condensate is drained overboard. The air is then returned to the cabin. A fan is used to blow the air over the cooling coil. The compressor requires a significant source of electrical power, so that an onboard engine driven generator or dockside supply of electrical power is required to operate the system.
A variety of portable systems are also available. These systems are similar to the window air conditioners commonly used to cool residential spaces. These systems use a similar process of compressing a refrigerant gas such as freon, and then permitting it to expand within the cooling coil of a heat exchanger. This expansion reduces the temperature of the gas, and allows it to extract heat from air flowing across the external surface of the cooling coil. The portable unit is placed over an open deck hatch, and air from the boat cabin is then pumped across the cooling coil and back into the cabin. The compressor power requirements on the portable unit require that the portable unit be powered by a dockside power supply, as an on-board generator is impractical on the smaller boats on which the portable system will be used.
It is also possible to use ice to cool air. Typically, the ice is stored inside an ice storage chamber having walls that allow heat transfer, as shown in FIG. 1. A fluid such as air is made to flow across the external surface of the wall of the ice storage chamber. This places the fluid in thermal communication with the ice in the chamber. Heat flows from the fluid into the ice, cooling the fluid and melting the ice. The major drawback to this system is that the ice is normally used in the form of chips or cubes which leave air spaces between ice and the wall of the storage chamber. These air spaces can act as insulation, reducing the efficiency of heat transfer across the wall.
As shown in FIG. 2, it is possible to modify the system of FIG. 1 to prevent the ice in the storage chamber from melting. A cooling fluid circulates through a coil within the ice storage chamber. This places the cooling fluid in heat transfer relationship with the ice in the storage chamber. Heat received by the ice from the first fluid flows into the cooling fluid, cooling the contents of the ice storage chamber and refreezing the ice. A compressor then compresses the cooling fluid, and allows it to expand into the coil within the ice storage chamber. This system has the drawback that a great deal of power is required to operate the compressor, making this system economically unattractive.
It is an object of this invention to provide an air conditioning system which does not require that a refrigerant gas be compressed by a compressor. Instead, an ice-cooled liquid is circulated through a cooling coil by a small, battery-powered pump, greatly reducing the power requirements.
It is a further object of this invention to provide an air conditioning system using a circulating ice-cooled liquid as a refrigerant rather than solid ice. This results in an improvement in the efficiency of heat transfer.